P0944: Hydraulic Pressure Unit Loss of Pressure
Do not keep driving
The car will not move and should be recovered rather than driven or towed with the wheels on the ground unless the handbook allows it. Ask for the hydraulic fluid level to be checked first — it is the cheapest cause and it is sometimes the only one.
What this code means
The actuation hydraulic system has lost pressure and cannot recover it. Where P0943 warns that pressure is being lost faster than it should, this is the state that warning was pointing at.
Without pressure the gearbox cannot operate the clutch or move the selection mechanism, so it cannot engage a gear at all. The vehicle typically ends up in neutral and stays there. Nothing mechanical inside the gearbox has necessarily failed — it simply has no means of being worked — which is why this is one of the more frustrating faults to experience: the car sounds perfectly healthy and will not move.
Causes divide into losing the fluid and failing to pressurise it. The first covers a burst line, a leaking actuator seal, or simply a level that has fallen far enough for the pump to draw air. The second covers the pump, its relay and its supply. Checking the fluid level is the first step and occasionally the whole answer.
Likely causes
Start here
- Hydraulic system leak · specialist
- Low hydraulic fluid level · easy
- Faulty hydraulic power unit · specialist
Less common
- Failed accumulator charge · specialist
- Faulty hydraulic pump relay · easy
- Leaking actuator seal · specialist
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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